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Thursday, 06 April 2023 03:00 PM

By the time light from the most distant galaxies reaches Earth, it has been stretched into the infrared part of the light spectrum by the expansion of the universe.

The James Webb Telescope’s NIRCam instrument has an unprecedented ability to detect this infrared light, allowing it to discover previously unseen galaxies, some of which could revolutionize astronomers’ understanding of the early universe.

In two studies published in the journal Nature Astronomy, astronomers announce that they have “undoubtedly discovered” four of the most distant galaxies ever observed.

Galaxies exist 300 to 500 million years after the Big Bang, 13 billion years ago, when the universe was only 2% of its current age.

Galaxies have a so-called “reionization epoch,” the time when the first stars are thought to have formed. This epoch followed the Cosmic Dark Ages caused by the Big Bang.

Astronomers now believe that light from these galaxies has been traveling toward Earth for more than 13.4 billion years, according to two new studies. The results show that these galaxies inhabited the Universe when it was less than 350 million years old, and indicate the rapid emergence of first-generation galaxies.

The discovery confirmed James Webb’s ability to carry out one of his most important tasks, which was to study the early universe through the long-traveled light as the universe’s expansion lengthened its wavelength. This broadening of light is called red shift. As light takes longer to travel, the universe expands toward the red end of the electromagnetic spectrum. This means that redshift can be used as a measure of distance, and early galaxies should have light that exhibits extreme redshift, with their light extending into the infrared range.

To date, the $10 billion telescope has identified several candidate galaxies at very high redshift, but these observations must be confirmed using spectroscopy.

Spectroscopy can be used to distinguish between early galaxies and nearby, recent galaxies that may share similar properties because spectroscopy can detect unique signatures of certain elements. Early galaxies were mostly composed of hydrogen and helium and lacked heavier elements such as oxygen, nitrogen and carbon. This is because it is not yet enriched by the heavy elements that are scattered when stars form through nuclear fusion and then die and go supernova.

Scientists’ analysis of data collected from the James Webb Near-Infrared Camera (NIRCam) and the Near-Infrared Spectroscopy (NIRSpec) instrument allowed them to determine four galaxies designated JADES-GS-z10-0, JADES-GS-z11-0. , and JADES-GS-z12-0 and JADES-GS-z13-0 actually have extreme redshifts of 10.3 to 13.2.

The name Jades refers to the James Webb Telescope’s JWST Advanced Deep Extragalactic Survey Instrument.

They came to this conclusion because the spectra of these galaxies lacked a clear signature of heavy elements like carbon, which James Webb sees when the universe was 300 to 500 million years old. (The universe is currently about 13.8 billion years old.)

JADES-GS-z13-0 is the most distant galaxy, formed 320 million years after the Big Bang, Stéphane Charlotte, a researcher at the Institute of Astrophysics in Paris and co-author of the two new studies, told AFP.

“For the first time we have detected galaxies 350 million years after the Big Bang, and we can be very confident about their amazing distances,” co-author and NIRCam science team member Brandt Robertson said in the release. We saw these early galaxies in such incredibly beautiful images.” Amazing is a special experience.”

The observations come from the first round of JADES observations pointed at a small region of the sky known as the Ultra Deep Field, which has been explored for nearly two decades by the Hubble Space Telescope. There are about 100,000 galaxies in this sky, each of which was discovered at some point in its history, perhaps billions of years ago.

The researchers used James Webb’s time over 10 days to study the extreme deep field with the NIRCam, observing it in nine different colors of infrared light.

This was followed by 28 hours of data collection over three days with the NIRSpec instrument. As such, James Webb has provided exceptionally sensitive and sharp images of the region, providing astronomers with the data they need to obtain precise measurements of the redshift of each galaxy and reveal the properties of the gas and stars within each.